(1) Standard gas
a. Quality / choice
This device uses span calibration gas as a standard gas for a sensitivity calibration.
Therefore, the accuracy and stability of its gas concentration level are important. Since gas
with a low concentration can be unstable, it is desirable to have one with higher
concentration. In addition, to ensure the reliability of the concentration level, standard gas
that has passed a legally established concentration inspection should be used for the
calibration. It is necessary to make sure to use the gas within the term of validity for its
use. If the time expires, the gas should be reexamined or replaced with new gas.
b. Replacement
All volume of the gas should not be consumed. When its remaining pressure becomes less than 10
kg/cm2, it is desirable to replace it.
It is recommended to buy new gas before replacing the old gas. It is necessary to consider the
waiting period between ordering and receiving new gas, the term of validity of the gas and the
remaining volume of gas to avoid running out of gas. In order to avoid running out of gas, it
is necessary to grasp how long it takes to get new gas after ordering it, and have records on
the due date for the replacement of gas and the remaining volume of gas.
c. Safety management
Since standard gas is under high pressure, it is necessary to obey laws prescribing
countermeasures against a fall of the gas cylinder, and pay attention to notes on management
and handling of the gas.
(2) Leak
When there is a drastic change in the span coefficient during the calibration process, you
should suspect that a leak is occurred. In such case, the suspected leak positions should be
carefully examined. In addition, the span coefficient should be checked and recorded at the
time of inspection to make a decision regarding the presence or absence of abnormality.
(3) Introduction of sample gas
If sample gas is introduced directly from the sample tube into the measurement device, the
fluctuations of instantaneous values becomes random. By installing a buffer tank of
approximately 20 liter in front of the sample gas introduction part, random indications can be
avoided.
